I picked up one of these when I snapped my wrist:http://www.rei.com/product/699801/dynaflex-lighted-gyro-power-ball
I actually picked it up at a GNC or something, for around $30. They're weighted gyroscopes, and you keep them spinning with wrist motion that should approximate what you need. You can get them with rpm-counters, and people compete to see how fast they can get them going.
I just try to make a habit out of using it while I'm percolating. I think I walked out of rehab with more flexibility than they were expecting.